How Can i Save my Love???

Hello EveryOne! I have a serious problem... i am in love with a girl for 5 years.. she also loves me a lot,,infact more than me.. We were very happy with each other & the girl is too much serious about me...She says she'll marry no one other than me... some days ago i found out that she already engaged with her cousin,,in indian sometimes parents engage their children when they are so young like 2-3 years... so now her parents r determined abt her marriage with cousin.. when i asked her,,she said she knew it but she doesnt like that boy,,i want 2 marry me...she says if i force her 2 marry that boy she would commit suicide,,she too serious abt me.. what should i do...her parents cant break up the engagement... i m so confused,,what should i do??? plz help me